automatically add generic validations to all models

generic_validations.rb

module ActiveRecord::Validations::ClassMethods
  #inspired by rails-schema_validations
  #https://github.com/gregwebs/rails-schema-validations
  def add_generic_validations
    begin
      self.columns.map do |column|            
        case column.type
        when :date
          validates_format_of_date(column.name) #this is a custom validation we defined (not part of rails)
        end
      end.compact
    rescue ActiveRecord::StatementInvalid => e
      #We may get an exception if the model uses the #set_table_name macro method because at this point of the model initialization
      #it doesn't yet have the correct table name to when it calls self#columns it is going to call it against the wrong table.
      #However this isn't that big of a deal because we have also aliased #set_table_name so that when it is called we will
      #re-run #validations_from_schema so that it will be run using the correct table name
      raise unless e.message =~ /relation "#{self.table_name}" does not exist/
    end
  end
end


ActiveRecord::Base.class_eval do
  class << self

    #enforce generic data type validations all the time on all models
    def inherited(subclass) #called when ActiveRecord::Base is inherited by another class...exactly what we need to add this functionality to all of our models
      super
      subclass.class_eval do
        add_generic_validations
      end
    end

    alias_method :old_set_table_name, :set_table_name
    def set_table_name(new_name)
      old_set_table_name(new_name)
      add_generic_validations
    end
    
  end
end